Pick out the wrong statement?

In practical operation of any furnace, zero oxygen percentage or theoretical CO2 percentage in flue gas is rarely achieved, because of________?

Ponchon-Savarit method analyses the fractional equipment based on________?

Most easily and cheaply available fibrous raw material for paper manufacture available in India is bamboo. The yield of pulp produced from fibrous raw material by mechanical process is about ________ percent?

Diameter to height ratio for a raschig ring is________?

White cast iron as compared to grey cast iron is ________?